1. Field of the Invention
This invention relates to a corrugated or convoluted laminated tube having a wall corrugated or convoluted along at least a portion thereof. The corrugated or convoluted laminated tube of this invention is suitable for use in, for example, a pipeline for automobile fuel (such as gasoline, gasoline containing alcohol, alcohol or hydrogen), or for fuel vapor.
2. Description of the Related Art
It has been usual to use a tube of a polyamide, or other resin, in a pipeline for automobile fuel, or fuel vapor. The resin tube has a low fuel permeability, and a high impact strength.
It has sometimes been the case to use a corrugated or convoluted resin tube having a corrugated or convoluted wall rather than a smooth one having a smooth wall, for the reasons as stated at (1) to (3) below:
(1) A corrugated or convoluted tube is superior to a smooth one in flexibility. Therefore, it can effectively absorb vibration and follow a fairly large relative displacement between the members connected to its opposite ends, respectively.
(2) A corrugated or convoluted tube is superior to a smooth one in deformability and expansibility. Therefore, it can tolerate any abnormal displacement occurring from, for example, the collision of the automobile, and can be bent at a relatively small angle to adapt itself to a limited space available when used for making a pipeline.
(3) In addition, it is superior to a smooth tube in collapsing strength owing to its structural features.
In order to ensure its merits as stated at (1) to (3) above, however, it is necessary for a corrugated or convoluted tube to have its corrugated or convoluted wall formed with a thickness which is smaller than the wall thickness of a smooth tube. Moreover, a corrugated or convoluted wall portion formed along a portion of a tube is smaller in thickness than any smooth wall portion thereof, since such a corrugated or convoluted wall portion is formed by corrugating a portion of the wall of a tube extruded with a uniform wall thickness.
Therefore, it is feared that a corrugated or convoluted tube may be more permeable to fuel because of the smaller thickness of its corrugated or convoluted wall.
Moreover, polyamide, or other particular resins are very likely to swell with fuel if they remain in contact with fuel, or fuel vapor at a high temperature for a long time. If such swelling occurs to a corrugated or convoluted wall of the resin tube, the expansion of its corrugations or convolutions causes the tube to undergo heavy axial expansion and thereby to be permanently deformed.
As a result, the corrugated or convoluted tube is likely to be deformed in such a way as to project from the space available for it and interfere undesirably with any component or part situated around it.